An English knight, Bowen (Dennis Quaid), mentors a Saxon prince, Einon (Lee Oakes), in the Old Code, the ideals of chivalry in the hope that he will become a better king than his tyrannical father Freyne (Peter Hric). When the king is killed while suppressing a peasant rebellion, Einon is mortally wounded by the peasant girl Kara (Sandra Kovacikova). Einon’s mother, Queen Aislinn (Julie Christie), has him taken before a dragon whom she implores to save the boy’s life. The dragon replaces Einon’s wounded heart with half of its own on the promise that Einon will rule with justice and virtue. However, Einon soon becomes more tyrannical than his father, enslaving the former rebels and forcing them to rebuild a Roman castle. Bowen believes that the dragon’s heart has twisted Einon, and swears vengeance on all dragons.